Heterojunction nanopore for sequencing

ABSTRACT

A technique is provided for performing sequencing with a nanodevice. Alternating graphene layers and dielectric layers are provided one on top of another to form a multilayer stack of heterojunctions. The dielectric layers include boron nitride, molybdenum disulfide, and/or hafnium disulfide layers. A nanopore is formed through the graphene layers and the dielectric layers. The graphene layers are individually addressed by applying individual voltages to each of the graphene layers on a one to one basis when a particular base of a molecule is in the nanopore. Each of the graphene layers is an electrode. Individual electrical currents are measured for each of the graphene layers as the particular base moves from a first graphene layer through a last graphene layer in the nanopore. The base is identified according to the individual electrical currents repeatedly measured for the base moving from the first through last graphene layer in the nanopore.

BACKGROUND

The present invention relates generally to nanodevices, and morespecifically, to a multi junction or heterojunction nanopore forsequencing molecules.

Nanopore sequencing is a method for determining the order in whichnucleotides occur on a strand of deoxyribonucleic acid (DNA). A nanopore(also referred to as pore, nanochannel, hole, etc.) can be a small holein the order of several nanometers in internal diameter. The theorybehind nanopore sequencing is about what occurs when the nanopore issubmerged in a conducting fluid and an electric potential (voltage) isapplied across the nanopore. Under these conditions, a slight electriccurrent due to conduction of ions through the nanopore can be measured,and the amount of current is very sensitive to the size and shape of thenanopore. If single bases or strands of DNA pass (or part of the DNAmolecule passes) through the nanopore, this can create a change in themagnitude of the current through the nanopore. Other electrical oroptical sensors can also be positioned around the nanopore so that DNAbases can be differentiated while the DNA passes through the nanopore.

The DNA can be driven through the nanopore by using various methods, sothat the DNA might eventually pass through the nanopore. The scale ofthe nanopore can have the effect that the DNA may be forced through thehole as a long string, one base at a time, like thread through the eyeof a needle. Recently, there has been growing interest in applyingnanopores as sensors for rapid analysis of biomolecules such asdeoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein, etc.Special emphasis has been given to applications of nanopores for DNAsequencing, as this technology holds the promise to reduce the cost ofsequencing below $1000/human genome.

SUMMARY

According to one embodiment, a method of performing sequencing with ananodevice is provided. The method includes providing alternatinggraphene layers and dielectric layers one on top of another to form amultilayer stack of heterojunctions, where the dielectric layers includeboron nitride layers, molybdenum disulfide layers, and/or hafniumdisulfide layers. The method includes forming a nanopore through each ofthe graphene layers and the dielectric layers, and individuallyaddressing each of the graphene layers by applying individual voltagesto each of the graphene layers on a one to one basis when a particularbase of a molecule is in the nanopore. Each of the graphene layers is anelectrode. The method includes respectively measuring individualelectrical currents for each of the graphene layers as the particularbase moves from a first graphene layer through a last graphene layer inthe nanopore, and determining an identification of the particular baseaccording to the individual electrical currents repeatedly measured forthe particular base moving from the first graphene layer through thelast graphene layer in the nanopore.

According to one embodiment, an apparatus for sequencing is provided. Ananodevice includes alternating graphene layers and dielectric layersone on top of another to form a multilayer stack of heterojunctions. Thedielectric layers include boron nitride layers, molybdenum disulfidelayers, and/o hafnium disulfide layers. The nanodevice includes ananopore through each of the graphene layers and the dielectric layers,and electrodes individually addressed to each of the graphene layers.The electrodes apply individual voltages to each of the graphene layerson a one to one basis when a particular base of a molecule is in thenanopore.

According to one embodiment, a method of forming a nanodevice forsequencing is provided. The method includes disposing alternatinggraphene layers and dielectric layers one on top of another to form amultilayer stack of heterojunctions, where a first graphene layer of thegraphene layers is initially disposed on an insulator that is disposedon a substrate. The dielectric layers include boron nitride layers,molybdenum disulfide layers, and/or hafnium disulfide layers. The methodincludes drilling a nanopore through each of the graphene layers and thedielectric layers, and disposing pairs of metal electrodes onto thegraphene layers at opposing ends, such that each of the graphene layersis individually connected to only one pair of metal electrodes.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIGS. 1A through 1G illustrate cross-sectional views of a process offorming a heterojunction nanopore in a nanodevice for sequencingaccording to an embodiment, in which:

FIG. 1A illustrates a cross-sectional view of a substrate and insulatorlayers of the nanodevice;

FIG. 1B illustrates a cross-sectional view of depositing/transferring a(first) graphene layer on top of the insulator layer;

FIG. 1C illustrates a cross-sectional view of depositing metalelectrodes;

FIG. 1D illustrates a cross-sectional view of depositing a firstdielectric layer on top of the first graphene layer;

FIG. 1E illustrates a cross-sectional view of depositing a secondgraphene layer on top of the first dielectric layer;

FIG. 1F illustrates a cross-sectional view of depositing second metalelectrodes on top of the second graphene layer and depositing a seconddielectric layer on top of the second graphene layer; and

FIG. 1G illustrates a cross-sectional view of the nanodevice afterrepeatedly performing operations in FIGS. 1B through 1F to deposit pairsof graphene layers and dielectric layers, along with corresponding metalelectrodes.

FIG. 2A illustrates a top view of the nanodevice according to anembodiment.

FIG. 2B illustrates the top view of the nanodevice with an upper layerlifted off to show underneath according to an embodiment.

FIG. 2C illustrates an example of a top view in which the metalelectrodes are staggered according to an embodiment.

FIG. 2D illustrates the example of the top view in which the metalelectrodes are staggered and an upper layer lifted off to showunderneath according to an embodiment.

FIG. 3 schematically illustrates a cross-sectional view of thenanodevice in a system for sequencing molecules according to anembodiment.

FIGS. 4A and 4B together illustrate a method of forming the nanodevicefor sequencing according to an embodiment.

FIG. 5 is a block diagram that illustrates an example of a computer(computer test setup) having capabilities, which may be included inand/or combined with embodiments.

DETAILED DESCRIPTION

As noted above, DNA (or RNA) sequencing is the process of determiningthe precise order of nucleotides within a DNA molecule. Knowledge of DNAsequences is very useful for basic biological research, and in numerousapplied fields such as diagnostic, biotechnology, forensic biology, andbiological systematics. Recently, nanopore devices attract intenseinterest as a promising structure for DNA sequencing. A nanoporetypically contains a thin film with a nano-sized pore in the film. Thethin film typically contains one metal layer to detect an electricalsignal and a few insulating layers for insulation and mechanicalsupport. When DNA passes through the nanopore, an electrical signal canbe detected. The electrical signal may be induced by the DNA blockage ofthe ionic current in the nanopore and/or induced by the electricalcharge on the DNA base. However, since the position and movement of theDNA in the ionic solution are highly random, the error rate for thisnanopore structure is typically very high.

Embodiments provide a (multi) heterojunction stack nanopore structurefor DNA sequencing. In each junction, there is one layer of metal (andone layer of an insulator). In this structure, each DNA base passesmultiple metal sensing layers (e.g., graphene) sequentially, such thatthe same DNA base is read multiple times as the DNA base passes throughthe nanopore. By analyzing (e.g., via a computer) the read out for eachbase statistically (i.e., the multiple reads of ionic (electrical)current measured for the same base at different intersections of thegraphene layer), the error rate can be significantly reduced. Morespecifically, embodiments propose multiple graphene/boron nitrideheterojunction stacks and/or multiple graphene/molybdenum disulfide(MoS₂) and/or hafnium disulfide layers heterojunction stacks to form thenanopore structure for DNA sequencing. Since graphene, boron nitride,and molybdenum disulfide can all be made atomically thin, the resolutionof the nanodevice is much higher than typical metal/oxide ormetal/nitride structure, and the heterojunction nanopore structurefurther improves the accuracy of the reading (for each base).

FIGS. 1A through 1G illustrate cross-sectional views of a process offorming a heterojunction nanopore for DNA sequencing according to anembodiment. The heterojunction nanopore is a nanodevice 100 that hasmultiple measuring points/junctions (each is the location between twoelectrodes) for repeatedly measuring the electrical current (i.e., thechange of electrical current when voltage is applied to the twoelectrodes) of the same base of a molecule (e.g., a DNA or RNAmolecule), as that base traverses through the nanopore.

FIG. 1A illustrates a cross-sectional view of the nanodevice 100. Thenanodevice 100 has a substrate 102. The substrate 102 may be a siliconsubstrate (e.g., a wafer). Insulator 104 may be grown on and/ordeposited on top of the substrate 102. Insulator 106 may be grown and/ordeposited on the bottom of the substrate 102. To form a cavity 108, theinsulator 106 and the substrate 102 are etched using lithography and awet etch as understood by one skilled in the art. The thickness ofinsulator 104 may be in the range of 20 to 40 nanometers (nm). Thethickness of insulator 106 may be in the range of 200 to 300 nanometers(nm). The insulators 104 and 106 may be any material that does notconduct electricity, such as silicon dioxide or silicon nitride.

FIG. 1B illustrates a cross-sectional view of depositing/transferring a(first) graphene layer 110A on top of the insulator layer 104. Themultiple layers of graphene are deposited (such that each side of thegraphene acts as an electrode as discussed further). The graphene layer110A may be patterned using lithography and oxygen plasma. As thegraphene layer 110A (along with subsequent graphene layers 110) can beas thin as 0.335 nm (nanometers), the spatial resolution of thisapproach can be 0.335 nm, which is sufficient spatial resolution for DNAsequencing purposes. The graphene was synthesized by a CVD method oncopper (Cu) foil. After graphene formation, PMMA (polymethylmethacrylate) was spin-coated on top of the graphene layer formed on oneside of Cu foil. This Cu foil was then dissolved in a copper etchant.The resulting graphene/PMMA layer was transferred to a SiO₂/Sisubstrate, where the PMMA was later dissolved in acetone.

FIG. 1C illustrates a cross-sectional view of depositing metalelectrodes 122A and 124A. The metal electrodes 122A and 124A (includingsubsequent metal electrodes) are deposited on and/or beside the graphenelayer 110A (or respective subsequent graphene layers), such that themetal electrodes 122A and 124A are in contact (i.e., physical andelectrical) with the graphene layer 110A. The metal electrode 122A is ontop of the left side of the graphene layer 110A and metal electrode 124Ais on the right side. The material of the metal electrodes 122A and 124A(including subsequent metal electrodes) may be include gold, titanium,palladium, tungsten, aluminum, etc., or combination of these metals.

FIG. 1D illustrates a cross-sectional view of depositing a (first)dielectric layer 112A (e.g., an insulating layer) on top of the firstgraphene layer 110A. The dielectric layer 112A may abut the metalelectrodes 122A and 124A. The dielectric layer 112A (and subsequentdielectric layers) may each be boron nitride, MoS₂, HfS₂, and/or anotherlayered two-dimensional (2D) material with a large band gap.

FIG. 1E illustrates a cross-sectional view of depositing a secondgraphene layer 110B on top of the first dielectric layer 112A. Thesecond graphene layer 110B is patterned such that it does not touch themetal electrodes 122A and 124A.

FIG. 1F illustrates a cross-sectional view of depositing a second metalelectrode 122B and a second metal electrode 124B on top of the secondgraphene layer 110B. The second metal electrode 122B is on the left sideof the graphene layer 110B while the second metal electrode 124B is onthe right side. A second dielectric layer 112 b is deposited on thesecond graphene layer 110B, and the dielectric layer 112B abuts themetal electrodes 122B and 124B.

The operations performed in FIGS. 1B through 1F are repeated totransfer/deposit other pairs of graphene layers and dielectric layers(as many as desired), along with depositing subsequent metal electrodes.FIG. 1G illustrates a cross-sectional view of nanodevice 100 withgraphene layers 110A through 110N, where 110N represents the lastgraphene layer. The nanodevice 100 also shows dielectric layers 112Athrough 112N, wherein 112N is the last dielectric layer.

The first metal electrode 122A through the last metal electrode 122N areshown in FIG. 1G, where the last metal electrode 122N is the last one ofthe metal electrodes 122 on the left side. The first metal electrode124A through the last metal electrode 124N are shown, where the lastmetal electrode 124N is the last one of the metal electrodes 124 on theright side.

Optionally, an insulator layer 114 is deposited on top of the lastdielectric layer 112N to touch the metal electrodes 122N and 124N. Thethickness of the insulator 114 is in the range of 10 to 40 nm. Thisthick insulator layer 114 provides additional protection and electricalisolation of the graphene layers 110 from the ionic buffer solution(solution 350 shown in FIG. 3).

Also, a nano-sized hole, nanopore 118, is drilled through the optionalinsulator 114, the graphene layers 110A through 110N, and the dielectriclayers 112A through 112N. The nanopore 118 can be drilled using atransmission electron microscope (TEM) or reactive ion etch (RIE).

FIG. 2A illustrates a top view of the nanodevice 100 according to anembodiment. In FIG. 2A, each of the metal electrodes 122A though 122Nand each of the metal electrodes 124A through 124N are shown in a line(from left to right). FIG. 2B shows the top view of a narrowed graphenestrip 205 (of the graphene layer 110N) underneath the dielectric layer112N. Note the graphene layers 110A through 110N are each patterned tobe narrower at the center (i.e., each has its own narrowed graphenestrip 205) where the nanopore 118 is located in order to increase thesensitivity of the respective graphene layers 110A through 110N (whenmeasuring electrical current with a DNA base present). The narrower thegraphene strip 205, the larger percentage change of the conductivityalong the graphene film (i.e., graphene layer 110) induced by the DNAbase. The graphene at the contact region (with respective electrodepairs 122 and 124) is wider in order to reduce contact resistance. Thegraphene strip 205 width at the center is in the range of 1 to 200 nm.The nanopore 118 size (diameter) is in the range of 0.5 to 100 nm, whichis to correspond to (i.e., fit within) the width of the graphene strip205. For example, if the graphene strip 205 is 1 nm wide, the nanopore118 has a diameter of 0.5. If the graphene strip 205 is 3 nm wide, thenanopore 118 may have a diameter of 1 nm (i.e., the diameter of thenanopore 118 is smaller than the width of the graphene strip 205).

Additionally, FIG. 2C illustrates an example of a top view in which themetal electrodes 122A through 122N and metal electrodes 124A through124N are staggered according to an embodiment. In this case, the metalelectrodes 122A through 122N and metal electrodes 124A through 124N arenot all lined up in a row. Rather, there is a first pair of metalelectrodes 122A and 124A in the front on the first graphene layer 110A,a second pair of metal electrodes 122B and 124B on the second graphenelayer 110B behind the first pair, and so forth until the last pair ofmetal electrodes 122N and 124N. For the staggered metal electrodes 122Athrough 122N, FIG. 2D shows the top view of the narrowed graphene strip205 (of the graphene layer 110N) underneath the dielectric layer 112N(as discussed above in FIG. 2B). The dielectric layer 112N has beenlifted off so view the narrowed graphene strip 205.

Now turning to FIG. 3, a schematic illustrates a cross-sectional view ofthe nanodevice 100 in a system 300 for sequencing (DNA and/or RNA)molecules according to an embodiment. The system 300 includes all thelayers of nanodevice 100 discussed herein in FIGS. 1 and 2.

The system 300 includes a top reservoir 305 attached and sealed to thetop of the nanodevice 100 and a bottom reservoir 310 attached and sealedto the bottom of the nanodevice 100. The top reservoir 305, bottomreservoir 310, and nanopore 118 are all filed with an electrolytesolution 350 (ionic or buffer solution) that conducts electricalcurrent. The electrolyte solution 350 may be a salt solution such asNaCl.

Electrode 312 is in the top reservoir 305, and electrode 313 is in thebottom reservoir 310. Electrodes 312 and 313 may be silver/silverchloride or platinum, for example.

Note that the graphene layers 110A through 110N may generally bereferred to as graphene layers 110, and dielectric layers 112A through112N may generally be referred to as dielectric layers 112. Also, metalelectrodes 122A through 122N may generally be referred to as metalelectrodes 122, and metal electrodes 124A through 124N may generally bereferred metal electrodes 124.

First metal electrodes 122A and 124A act as a first pair of electrodeselectrically connected to the graphene layer 110A. Second metalelectrodes 122B and 124B act as a second pair of electrodes electricallyconnected to the graphene layer 110B. Similarly, last metal electrodes122N and 124N act as the last pair of electrodes electrically connectedto the graphene layer 110N.

A molecule 355, such as a DNA molecule for example, is in the topreservoir 305. Each base/nucleotide 357 of the molecule 355 is depictedas a solid oval connected to one another by a backbone (connectingline). The DNA molecule 355 may be a negatively charged molecule. TheDNA molecule 355 is moved to (i.e., captured at the entrance (the top ofnanopore 118) and through the nanopore 118 by applying a voltage from avoltage source 360 across electrodes 312 and 313. An electric fieldgenerated by the voltage of the voltage source 360 controllably drivesthe DNA molecule 355 through the nanopore 118 at a desired rate, e.g.,by pulsating (i.e., repeatedly turning on and off) the voltage source360. The voltage generates an electric field across the nanodevice 100(via electrodes 312 and 313) to move the DNA molecule 355 as desired.

Once the DNA molecule 355 is in the nanopore 118, the respectivevoltages of voltage sources 370A, 370B, through 370N are turned on toindividually generate electrical current that is respectively measuredby corresponding ammeters 375A, 375B, through 375N.

For example, assume that a particular base 357A is in the nanopore 118between the left and right side of the last graphene layer 110N. Thevoltage source 370N is applied via the (last) pair of metal electrodes122N and 124N to generate electrical current. The electrical currentflows from the last voltage source 370N, into last metal electrode 122N,into the left side of the last graphene layer 110N, into the nanopore118 to interact with the particular base 357A, out through the rightside of the last graphene layer 110N, and out through the last metalelectrode 124N to be measured by the last ammeter 375N. This electricalcurrent (signature) may be stored by a computer 500 for comparison (andeventual identification) against subsequent electrical currentmeasurements of the same particular base 357A by the remaining graphenelayers.

Now, the particular base 357A is moved to the next graphene layer whichis graphene layer 110B (in this example), so that a second electricalcurrent measurement may be performed via ammeter 375B. In this case, thevoltage of the voltage source 370B is applied via the pair of metalelectrodes 122B and 124B to generate electrical current. The electricalcurrent flows from the voltage source 370B, into metal electrode 122B,into the left side of the last graphene layer 110B, into the nanopore118 to interact with the particular base 357A, out through the rightside of the graphene layer 110B, and out through the metal electrode124B to be measured by the ammeter 375B. This electrical current(signature) may also be stored by the computer 500 for comparison (andeventual identification) against past and future electrical currentmeasurements of the same particular base 357A.

By analogy, the same process occurs when the particular base 357A ismoved between the left and right sides of the graphene layer 110A in thenanopore 118. The voltage of the voltage source 370A is applied tomeasure the electrical current when the particular base 357A is presentin the nanopore 118 between the left and right sides of the graphenelayer 110A. The electrical current is measured by the ammeter 375A andis again stored in the computer 500. Each of the electrical currentsmeasured for the particular base 357A are compared (e.g., by thecomputer 500 and/or an operator) against known electrical currents(signatures) that respectively identify bases (such as bases A, G, C,and T) such that the individual electrical currents (which should be thesame or statistically the same) for the particular base 357A are matchedand identified accordingly.

Note that the voltages sources 370, ammeters 375, and voltage source360, along with individual electric current reading, can be implementedand controlled by a computer system 500 (test setup equipment) discussedin FIG. 5.

Although only three graphene layers 110 (which act as sensors) areconnected to respective voltage sources 370 and ammeters 375 by wire andmetal electrodes, there may be more than three graphene layers 110(along with respective equipment and additional layers). For example,there may be 4, 5, 6, 7 . . . 10 or more graphene layers 110 (eachrespectively connected to its own metal electrodes 122 and 124, wire,voltage source 370, and ammeter 375) with each graphene layer having acorresponding dielectric layer 112 on top, as shown in FIGS. 1-3. Eachof these, e.g., 10 graphene layers is utilized to repeatedly measure andgenerate individual electrical currents for the particular bases 357A,so that the particular base 357A can be matched.

FIGS. 4A and 4B together are a method of forming the nanodevice 100 forsequencing according to an embodiment. Reference can be made to FIGS.1-3 discussed herein (including FIG. 5 below).

Alternating graphene layers 110A-110N and dielectric layers 112A-112Nare deposited/provided one on top of another to form a multilayer stackof heterojunctions at block 405. Each junction of the heterojunctions isthe location in the nanopore 118 between, for example, the left side andright side of graphene layer 110 (graphene layer 110A) at which theelectrical current for the base 357 is measured.

The dielectric layers 112 include at least one of boron nitride layers,molybdenum disulfide layers, and/or hafnium disulfide layers at block410. In one case, each of the dielectric layers 112A-112N is boronnitride layer(s). In another case, each of the dielectric layers112A-112N is molybdenum disulfide layer(s) (MoS₂). In one case, thedielectric layers 112A-112N may be alternating dielectric layers ofboron nitride layer(s) and (then next) molybdenum disulfide layer(s).

A nanopore 118 is formed through each of the graphene layers 110 and thedielectric layers 112 (and optionally the insulating layer 114) at block415.

Each of the graphene layers 110 is individually addressed by applyingindividual voltages (from respective voltage sources 370A-370N) to eachof the respective graphene layers 110A-110N on a one to one basis when aparticular base 357A of the molecule 355 is in the nanopore 118 at block420. Each of the graphene layers 110A-110N is an electrode with ajunction (for measuring electrical current change when the base 357 isin the junction) in the nanopore 118.

Individual electrical currents are respectively (repeatedly) measuredfor each of the graphene layers 110A-110N as the particular base 357Amoves from a first graphene layer 110A through a last graphene layer110N in the nanopore 118 (each base 357 is repeatedly measured (e.g., 3,4, 5, 7, 9 times) at the various junctions in the nanopore 118) at block425.

An identification of the particular base 357A is determined (by computer500) according to the individual electrical currents repeatedlyread/measured for the particular base 357A moving to the first graphenelayer 110A (and measured) through the last graphene layer 110N (andmeasured) in the nanopore 118 (such that the individual electricalcurrent for the particular base is measured at each junction) at block430.

Determining the identification of the particular base according to theindividual electrical currents being repeatedly read for the particularbase is based on measured values of the individual electrical currentsbeing a same or nearly the same. These measured values are matched(e.g., by the computer 500) to known (predetermined) electrical currentvalues for known bases so that the particular base 357A can beidentified as, e.g., base A, G, C, or T. Note that when the value of oneof the individual electrical currents measured for the particular base357A is off (e.g., deviates from the nearest/closest value of any of theindividual electrical currents (which can be less than or greater than)by a predetermined amount or more (e.g., 0.5 picoamperes (pA), 0.8 pA,and/or 1 pA or more) from the other measured values of the electricalcurrents for the particular base 357A, the electrical current value thatis off the predetermined amount (or more) is dropped and is not utilizedas a value to match the known (predetermined) electrical current valuesfor known bases. Instead, the remaining individual electrical currentvalues (of the particular base 357A) are utilized by the computer 500 tomatch one of the known (predetermined) electrical current values forbase A, G, C, or T.

The individual electrical currents each correspond to the (same)particular base 357A at different locations (i.e., different junctionsbetween the left side and right side of respective graphene layers 110)in the nanopore 118. The individual electrical currents correspond tomeasuring via the graphene layers as the electrodes on a one to onebasis, such that no graphene layer 110 measures the particular base 357Amore than once (because the base moves on through the nanopore 118 to bemeasured by the next graphene layer 110). The number of the individualelectrical currents measured for the particular base 357A at thedifferent locations (each junction) in the nanopore 118 equals thenumber of the graphene layers 110A-110N.

The dielectric layers 112 may include layers of a combination of theboron nitride layers, the molybdenum disulfide layers, (and/) or hafniumdisulfide layers in an alternating manner. The boron nitride layers eachhave one or few mono-layers of boron nitride. Each mono-layer of boronnitride has a thickness of 0.3 to 0.5 nanometers. The molybdenumdisulfide layers each have one or few mono-layers of molybdenumdisulfide. Each mono-layer of molybdenum disulfide has a thickness of0.6 nanometers to 0.8 nanometers. The individual dielectric layers 112are each atomically thin insulators. These materials (boron nitride,molybdenum disulfide, and hafnium disulfide) have a layered structuresimilar to graphite. Within each layer, atoms are bound by strongcovalent bonds, whereas the layers are held together by weak van derWaals forces. Therefore atomically thin layer(s) (i.e., a mono-layers)can be obtained easily by exfoliation or chemical synthesis. Theresulting atomically thin layers are continuous and mechanically strong.Boron nitride is an insulator; MoS₂ and HfS2 are wide band gapsemiconductors.

FIG. 5 illustrates an example of a computer 500 (e.g., as part of thecomputer test setup for testing and analysis) which may implement,control, and/or regulate the respective voltages of the voltage sources,respective measurements of the ammeters, and display screens fordisplaying various electrical current amplitude (including ioniccurrent) as discussed herein. The computer 500 also stores therespective electrical current amplitudes of each base tested andmeasured to be compared against the baselines current amplitudes ofvarious known bases (predetermined in advance), which is utilized toidentify the bases of the tested/target molecule.

Various methods, procedures, modules, flow diagrams, tools,applications, circuits, elements, and techniques discussed herein mayalso incorporate and/or utilize the capabilities of the computer 500.Moreover, capabilities of the computer 500 may be utilized to implementfeatures of exemplary embodiments discussed herein. One or more of thecapabilities of the computer 500 may be utilized to implement, toconnect to, and/or to support any element discussed herein (asunderstood by one skilled in the art) in FIGS. 1-4. For example, thecomputer 500 which may be any type of computing device and/or testequipment (including ammeters, voltage sources, current meters,connectors, etc.). Input/output device 570 (having proper software andhardware) of computer 500 may include and/or be coupled to thenanodevices and structures discussed herein via cables, plugs, wires,electrodes, patch clamps, electrode pads, etc. Also, the communicationinterface of the input/output devices 570 comprises hardware andsoftware for communicating with, operatively connecting to, reading,and/or controlling voltage sources, ammeters, and current traces (e.g.,magnitude and time duration of current), etc., as discussed andunderstood herein. The user interfaces of the input/output device 570may include, e.g., a track ball, mouse, pointing device, keyboard, touchscreen, etc., for interacting with the computer 500, such as inputtinginformation, making selections, independently controlling differentvoltages sources, and/or displaying, viewing and recording currenttraces for each base, molecule, biomolecules, etc.

Generally, in terms of hardware architecture, the computer 500 mayinclude one or more processors 510, computer readable storage memory520, and one or more input and/or output (I/O) devices 570 that arecommunicatively coupled via a local interface (not shown). The localinterface can be, for example but not limited to, one or more buses orother wired or wireless connections, as is known in the art. The localinterface may have additional elements, such as controllers, buffers(caches), drivers, repeaters, and receivers, to enable communications.Further, the local interface may include address, control, and/or dataconnections to enable appropriate communications among theaforementioned components.

The processor 510 is a hardware device for executing software that canbe stored in the memory 520. The processor 510 can be virtually anycustom made or commercially available processor, a central processingunit (CPU), a data signal processor (DSP), or an auxiliary processoramong several processors associated with the computer 500, and theprocessor 510 may be a semiconductor based microprocessor (in the formof a microchip) or a macroprocessor.

The computer readable memory 520 can include any one or combination ofvolatile memory elements (e.g., random access memory (RAM), such asdynamic random access memory (DRAM), static random access memory (SRAM),etc.) and nonvolatile memory elements (e.g., ROM, erasable programmableread only memory (EPROM), electronically erasable programmable read onlymemory (EEPROM), programmable read only memory (PROM), tape, compactdisc read only memory (CD-ROM), disk, diskette, cartridge, cassette orthe like, etc.). Moreover, the memory 520 may incorporate electronic,magnetic, optical, and/or other types of storage media. Note that thememory 520 can have a distributed architecture, where various componentsare situated remote from one another, but can be accessed by theprocessor 510.

The software in the computer readable memory 520 may include one or moreseparate programs, each of which comprises an ordered listing ofexecutable instructions for implementing logical functions. The softwarein the memory 520 includes a suitable operating system (O/S) 550,compiler 540, source code 530, and one or more applications 560 of theexemplary embodiments. As illustrated, the application 560 comprisesnumerous functional components for implementing the features, processes,methods, functions, and operations of the exemplary embodiments.

The operating system 550 may control the execution of other computerprograms, and provides scheduling, input-output control, file and datamanagement, memory management, and communication control and relatedservices.

The application 560 may be a source program, executable program (objectcode), script, or any other entity comprising a set of instructions tobe performed. When a source program, then the program is usuallytranslated via a compiler (such as the compiler 540), assembler,interpreter, or the like, which may or may not be included within thememory 520, so as to operate properly in connection with the O/S 550.Furthermore, the application 560 can be written as (a) an objectoriented programming language, which has classes of data and methods, or(b) a procedure programming language, which has routines, subroutines,and/or functions.

The I/O devices 570 may include input devices (or peripherals) such as,for example but not limited to, a mouse, keyboard, scanner, microphone,camera, etc. Furthermore, the I/O devices 570 may also include outputdevices (or peripherals), for example but not limited to, a printer,display, etc. Finally, the I/O devices 570 may further include devicesthat communicate both inputs and outputs, for instance but not limitedto, a NIC or modulator/demodulator (for accessing remote devices, otherfiles, devices, systems, or a network), a radio frequency (RF) or othertransceiver, a telephonic interface, a bridge, a router, etc. The I/Odevices 570 also include components for communicating over variousnetworks, such as the Internet or an intranet. The I/O devices 570 maybe connected to and/or communicate with the processor 510 utilizingBluetooth connections and cables (via, e.g., Universal Serial Bus (USB)ports, serial ports, parallel ports, FireWire, HDMI (High-DefinitionMultimedia Interface), etc.).

In exemplary embodiments, where the application 560 is implemented inhardware, the application 560 can be implemented with any one or acombination of the following technologies, which are each well known inthe art: a discrete logic circuit(s) having logic gates for implementinglogic functions upon data signals, an application specific integratedcircuit (ASIC) having appropriate combinational logic gates, aprogrammable gate array(s) (PGA), a field programmable gate array(FPGA), etc.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of onemore other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While the preferred embodiment to the invention had been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

1-10. (canceled)
 11. An apparatus for sequencing, the apparatuscomprising: a nanodevice including: alternating graphene layers anddielectric layers one on top of another to form a multilayer stack ofheterojunctions, wherein the dielectric layers include at least one ofboron nitride layers, molybdenum disulfide layers, and hathium disulfidelayers; and a nanopore through each of the graphene layers and thedielectric layers; and electrodes individually addressed to each of thegraphene layers, the electrodes applying individual voltages to each ofthe graphene layers on a one to one basis when a particular base of amolecule is in the nanopore.
 12. The apparatus of claim 11, furthercomprising: a test setup, wherein the test setup is configured torespectively measure individual electrical currents for each of thegraphene layers as the particular base moves from a first graphene layerthrough a last graphene layer in the nanopore; and wherein the testsetup is configured to determine an identification of the particularbase according to the individual electrical currents repeatedly measuredfor the particular base moving from the first graphene layer through thelast graphene layer in the nanopore.
 13. The apparatus of claim 12,wherein determining the identification of the particular base accordingto the individual electrical currents repeatedly measured for theparticular base is based on measured values of the individual electricalcurrents being a same or nearly the same.
 14. The apparatus of claim 12,wherein the individual electrical currents each correspond to theparticular base at different locations in the nanopore.
 15. Theapparatus of claim 12, wherein the individual electrical currentscorrespond to measuring via the graphene layers as the electrodes on aone to one basis, such that no graphene layer measures the particularbase more than once.
 16. The apparatus of claim 12, wherein a number ofthe individual electrical currents measured for the particular base atdifferent locations in the nanopore equals a number of the graphenelayers.
 17. The apparatus of claim 11, wherein the boron nitride layerseach have one or few mono-layers of boron nitride; wherein eachmono-layer of the boron nitride has a thickness of 0.3 nanometers to 0.5nanometers; wherein the molybdenum disulfide layers each have one or fewmono-layers of molybdenum disulfide; and wherein each mono-layer of themolybdenum disulfide has a thickness of 0.6 nanometers to 0.8nanometers. 18-20. (canceled)